An improved technique for obtaining well-spread metaphases from plants with numerous large chromosomes.

Preparations that contain well-spread metaphase chromosomes are critical for plant cytogenetic analyses including chromosome counts, banding procedures, in situ hybridization, karyotyping and construction of ideograms. Chromosome spreading is difficult for plants with large and numerous chromosomes. We report here a technique for obtaining cytoplasm-free, well-spread metaphases from two Amaryllidaceae species: Sprekelia formosissima (2n = 120) and Hymenocallis howardii (2n = 96). The technique has three main steps: 1) pretreatment to cause chromosome condensation, 2) dripping onto tilted slides coated with a thin layer of pure acetic acid and 3) application of steam and acetic acid to produce cytoplasmic hydrolysis, which spreads the chromosomes.

[Regionalization]. / Regionalización.

Health services regionalization is analyzed in its concept, components, characteristics and variations through literature review of experiences in different countries. It is concluded that regionalization means ordering or reordering resources and services within an area, provided that physical installations and personnel are already organized in order to assure health services at the highest quality. Those services must be economical, accesible and established in a comprehensive, coherent set with different levels of care in order to meet patients' needs. A regionalization model based on silos is presented, including functions, strategies and policies. Reasons to encourage the regionalization are also presented, such as the decrease in costs, increasing of program effectiveness and the potential development of the regionalized areas.

[Mortality from tetanus in children less than 1 year of age, Mexico, 1970-1982]. / La mortalidad por tétanos en menores de un año, México 1970-1982.

The results of a study about mortality by tetanus in Mexican children under one year of age, during the 1970-1982 period, are reported. This age-group was subdivided in three, as follows: perinatal (less than 7 days), neonatal (less than 29 days) and postneonatal (29 to 364 days). Mortality by tetanus in children under one year of age showed a decreasing trend during the mentioned period, and this was most pronounced from 1979, because of changes in the codification of mortality by tetanus in this group of age. On the other hand, it was found that the greatest proportion of deaths by tetanus happened in the under one year of age group, and particularly in the neonatal group (less than 29 days). The geographic distribution of tetanus in Mexico was studied later, and showed a predominant incidence of the disease in coastal states of the country; an additional finding in this investigation was the displacement of the disease from the Pacific strip to the Gulf of Mexico. Finally, the mortality differentials by sex were studied, and showed that males were the most affected in the three age groups. We cannot explain this finding at the time.

[Toward an operational definition of the health-illness process]. / Hacia una definición operativa del proceso salud-enfermedad.

The article reviews the meaning of the terms health and illness, and seeks to define those aspects of these concepts that are most related to the supply of health services. After considering the process of health and illness and its implications for the the planning of health care, the authors express the need for conceptual models of health and environment (physical and social) that can be related to the objectives of the health system. As a part of the search for a better population data base, certain health and welfare indicators are suggested. The discussion concludes with a brief strategy for the operationalization of the health/illness continuum as a part of the planning for a national health service.